Semantic MediaWiki versions from 3.0.0 up to but not including 7.4.1 contain a denial of service vulnerability in the ElasticStore and SPARQLStore components. This flaw arises from the ConceptDescriptionInterpreter classes re-expanding concepts without memoization or limiting expansion, allowing users with page-edit rights to create acyclic chains of Concept: pages that cause excessive CPU and memory consumption during queries. The vulnerability can be triggered via concept page views, Special:Ask, or the api.php action=ask endpoint.